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From: Apache Wiki
To: core-commits@hadoop.apache.org
Date: Thu, 05 Mar 2009 23:44:45 -0000
Message-ID: <20090305234445.23504.11608@aurora.apache.org>
Subject: [Hadoop Wiki] Trivial Update of "Hbase/DesignOverview" by EvgenyRyabitskiy
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Dear Wiki user,
You have subscribed to a wiki page or wiki category on "Hadoop Wiki" for change notification.
The following page has been changed by EvgenyRyabitskiy:
http://wiki.apache.org/hadoop/Hbase/DesignOverview
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[[Anchor(datamodel)]]
= Data Model =
- HBase uses a data model very similar to that of Bigtable. Applications store data rows in labeled tables. A data row has a sortable row key and an arbitrary number of columns. The table is stored sparsely, so that rows in the same table can have widely varying numbers of columns.
+ Applications store data rows in labeled tables. A data row has a sortable row key and an arbitrary number of columns. The table is stored sparsely, so that rows in the same table can have widely varying numbers of columns.
A column name has the form ''":"'' where and can be arbitrary byte arrays. A table enforces its set of s (called ''"column families"''). Adjusting the set of families is done by performing administrative operations on the table. However, new s can be used in any write operation without pre-announcing it. HBase stores column families physically close on disk, so the items in a given column family should have roughly the same read/write characteristics and contain similar data.
Only a single row at a time may be locked by default. Row writes are always atomic, but it is also possible to lock a single row and perform both read and write operations on that row atomically.
An extension was added recently to allow multi-row locking, but this is not the default behavior and must be explicitly enabled.
+
+ More details are here [:Hbase/DataModel: The HBase/Bigtable Data Model]
[[Anchor(conceptual)]]
== Conceptual View ==